Electron discharge apparatus



M 1951 A. E. ANDERSON ELECTRON DISCHARGE APPARATUS 2 Sheets-Sheet 2Filed Sept. 6, 1947 BEAM PATH CHANNEL owrur IN VENT OR [70 Wall SAW 0THVOLTAGE 43 CRCULAR SWEEP SOURCE wear A. EA/VDERSON ATTORNEY PatentedSept. 11, 1951 ELECTRON DISCHARGE APPARATUS Alva Eugene Anderson,Chathani, N. J assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application September 6,1947, Serial No. 772,538 12 Claims. (o1. 315-21) This invention relatesto electron discharge apparatus and more particularly to cathode raydevices especially suitable for use as receivers in multichannel or timedivision multiplex communication systems.

Such devices comprise, in general, a plurality of target electrodes, anelectron gun for projecting an electron beam toward the targetelectrodes, and a deflection system for directing the beam so that itimpinges upon the target electrodes in 1 succession thereby to close orenergize output channels associated with the electrodes.

Heretofore, in order to obtain effective segregation of the severaltarget electrodes to minimize or eliminate cross-talk between thechannels, it

has been necessary to provide a substantial space between adjacenttarget electrodes. This results in substantial limitation upon theusable portion of each deflecting cycle, for the spacing or guard spaceinvolved represents lost time. Further, it limits the number or size, orboth, of target electrodes that can be utilized in a device of specifieddimensions. Limitation of the number of target electrodes restricts thenumber of channels that may be employed. Limitation of the electrodesize may restrict the power that can be translated.

One general object of this invention is to improve cathode ray devicesfor multiplex communication systems.

More specifically, objects of this invention are to reduce the guardspace in such devices, increase the number of target electrodes whichmay be incorporated in a device of given dimensions, assure goodelectrical segregation of the several output channels, enhance the powercapacity and output, and facilitate the construction of cathode raydevices including a multiplicity of target electrodes.

In accordance with one general feature of this invention, the aforenotedand other objects are realized by a particular construction of targetelectrode assembly and by correlation of the electron beam deflectionsystem therewith.

More particularly, in accordance with features of this invention, in acathode ray device for multiplex systems, the assembly above mentionedcomprises a plurality of elongated target electrodes mounted in circulararray and extending obliquely with respect to radii of a referencecircle, the electrodes being disposed in partly overlapping relationrelative to the radii. The deflection system is constructed and arrangedtoproduce a beam trace at the electrode assembly of circular saw-toothform, alternate sections of the trace being parallel to or coincidentwith the longitudinal axis of respective electrodes and the othersections of thetrace being radial or substantially so. Advantageously,the beam is controlled so that it is on during the sweep thereof alongeach target electrode and is extinguished during the radial portions ofthe beam trace.

- The beamcurrent to. any target electrode may be utilized directly asthe output. Advantageously, however, the target electrodesareconstructed to have a coefiicient of secondary emission greater thanunity, and a collector electrode structure is provided for receiving thesecondary electrons emanating from the target. electrodes. The outputcurrent at each target electrode, then, is proportional to thedifierence between the beam current to the electrode and the secondaryelectron current away therefrom. The collector electrode structureincludes conductive barriers or shields interposed between adjacenttarget electrodes.

The invention and the above-noted and other features thereof will beunderstood more clear:- ly and fully from the. following detaileddescriptionwith reference to the accompanying drawing in which: V

Fig. 1 isan elevational view mainly in section of an electron dischargedevice illustrative of one embodiment of this invention; 7

Fig. 2 is a fragmentary plan viewshowing details of the target and.collector electrode assembly. included in the device illustrated inFig.1; Fig. 3 is a view insection taken along line 3-3 of Fig. 2;

Fig. 4 is a diagram illustrating the beam path or trace at the targetand collector electrode assembly; and

Fig. 5 is a circuit schematic illustrating one manner inwhich the deviceshown in Fig. 1 may be operated. Referring now to the drawing, theelectron discharge device shown in Fig. 1 comprises an evacuated,vitreous enclosing vessel l0 having an external stem II at one end,fromwhich an electron gun and deflector platev assembly is supported..The electrongun, which may be of generally conventional construction,comprises a cathode, illustrated at l2 in Fig. 5, which is encompassedby a cylindrical anode l3, a cylindrical control electrode l4, and acylindrical focussing electrode IS, the several electrodes beingconnected to respective terminals l6 upon a base H by leading-inconductors I8. The control electrode l4 and focussing anode I5 areassociated in coaxial relation by discs or platforms l9 and 2 0mechanically. coupled in fixed relation by in- .sulating masses orbodies 2|. 7.

Supported from the disc or platform 20 by insulating bodies 22 are twopairs of deflector plates 23 and, the two pairs being in space-quadrature and the plates being connected electrically to respectiveterminals l6 by associated leading-in conductors I8. Also supported bythe disc or platform 20 and coaxial with the gun electrodesis afrusto-conical metallic shield 25.

'it to the disc 3|.

the terminals 36. In the operation of the device, as illustrated in Fig.5, the electrodes constituting the electron 3 A plurality of rigid,insulating supports or rods 26 are secured to the shield 25 by U-shapedbrackets 21 affixed to the shield, as by welding, and to the rods as bymasses 28 of insulating cement. The supports or rods 26 mount afrustoconical deflecting electrode 29 and a metallic shield 30, bothcoaxial with the electron gun and V secured to the rods by brackets 21and masses 28 of insulating cement.

The shield 39 mounts a target and collector electrode assembly which, asshown in detail in Figs. 2 and 3, comprises a circular insulating disc3|, for example of mica, seated upon an internal flange or shoulder 32on the shield. The assembly includes also a plurality, for exampletwentyfo'ur, of identical target electrodes disposed at equal angles tocorresponding'radii of the disc 3|. each of the target electrodescomprising 2. rectangular portion 33A and an inwardly tapered portion333 and having bent end parts 34 defining locking tabs extending throughslots in the disc 3|. The target electrodesare of a material, such as,for example silver-magnesium alloy, having a coeflicient of secondaryemission greater than unity. Alternatively, the faces of the targetelectrodes toward. the electron gun may be coated with a material havinga high secondary emission coeflicient. Individual electrical connectionto these electrodes may be established by leading-in conductors 35 whichare sealed through the side wall of the enclosing vessel l and areconnected to terminals 36 carried by an insulating support 31 within adished'" shell 38 secured to the vessel I0. 7.

The assembly includes also a plurality of metallic shield-collectorelectrode elements, onefor each of the target electrodes. Each of theseelements comprises a base portion 39 seated upon the insulating disc 3|and aflixed to the respective target electrode by masses 4B ofinsulating cement, and comprises also an integral upstanding Z-shapedportion 4|, the intermediate part of which, as shown in Fig. 2, extendsbetween adjacent target electrodes. The several shield-collectorelements are tied together electrically by connecting tabs 42 and areconnected to one of the terminals 36 by a leading in conductor 43.

The target electrodes and shield-collector elements, it will be noted,constitute a plurality, e. g. 24, of substantially identical unitsmounted in circular array coaxial with the electron gun. As will bepointed out in detail presently, the elements function to collectsecondary electrons emanating from the target electrodes. Also, theseelements and specifically, the upstanding portions 4| thereof, shieldand segregate adjacent target electrodes from one another. Particularlyadvantageously the elements 39, 4| are treated or coated to minimizesecondary electron emission therefrom.

Extending coaxially within the deflector electrode 29 is a second,cylindrical deflector electrode 44 which is supported from the disc 3|by flanged collars 45 affixed to the electrode 44 and locking deflectorelectrode 44 may be established by way of a leading-in conductor 46connected to one of gun are energized appropriately to produce aconcentrated electron beam which is projected between the defiectorplates-'23 and 24. These plates are energized from a source 41 to"produce a circular motion of the beam. The coaxial de- Electricalconnection to the flector electrodes 29 and 44 are energized from asource 48 applying a saw-tooth voltage between them. The two deflectingvoltages, that is, those due to the sources 41 and 48, are correlated sothat the beam trace or path at the target electrodes 33 is of circularsaw-tooth form as indicated by the dotted line P in Fig. 4. Theshieldcollector elements 39, 4| are operated at a poten tial positivewith respect to both the cathode l2 and the target electrodes 33, andthe shield 30 may be tied directly to these elements as illustrated.Individual output channels each including an output resistor 49 andseries condenser 50 are connected to the target electrode 33, only onesuch channel being illustrated in Fig. 5. Alternatively,transformer-type output coupling may be used.

The multiplex signal to be translated, which may be of any one of anumber of forms, such as amplitude modulated or pulse length .modulated,is applied to the control electrode l4 by way of a suitable inputcircuit 5|, the beam sweep cycle being synchronized, of course, with thetransmitter producing the multiplex signal .so that each non-radialsection such as AB in Fig. 4 of the beam trace corresponds to the periodof.a respective transmitter channel. Advantageously, the input circuit5| includes appropriate apparatus for extinguishing the. beam during theperiod corresponding to each radial section, such as BA1, of the beamtrace.

The input signal controls the intensity of the beam and, thus, the beamcurrent to each target electrode is varied in accordance with therespective time segment of the multiplex input signal. Whenever the beamimpinges upon one of the target electrodes, secondary electrons flowtherefrom to the associated collector element 39, 4|. The current in theoutput channel coupled to this electrode is determined, then, by thediiference between the beam current to this electrode and the secondaryelectron current away therefrom.

It will be appreciated that because of the arrangement of the targetelectrodes 33 and the form of the beam trace, and particularly in caseswhere the beam is extinguished for the periods corresponding to theradial sections, such as BA1, of the trace, electronic segregation ofthe several target electrodes is realized without substantial sacrificeof space in the target electrode assembly. Stated in another way, theguard space required is minimized and there is a mini mum of lost orwasted time between channels during each sweep cycle. A large proportionof each sweep cycle, therefore, is usable for the translation of signalsso that a large ratio of duty" time to guard time obtains. Further,because of the factors mentioned, it will-be noted that the targetelectrodes may be closely spaced physically so that a large number ofsuch electrodes may be utilized in any given and relatively small space.Also, the target electrodes may be large, having, for example, a widthsomewhat greater than the beam diameter and a length several times thebeam diameter, whereby large output currents may be attained andwhereby, further, the relative currents in the several channels areindependent of the transverse current distribution in the electron beam.

It will be appreciated additionally that the several target electrodesare highly shielded from one another and from external fields. Straysecondary electrons, such as may emanate from the elements 4| are drawnto the shield 30, so that distortion is minimized.

Although in the construction heretofore described secondary electronemissive targets of particular form and arrangement and associatedcollector elements are employed, it will be appreciated that theprinciples of the invention may be utilized also in devices wherein anapertured plate between the electron gun and the targets is employed. Inone such construction, for example, a plate or mask having apertures ofthe form and arrangement of the targets as illus-' trated in Fig. 4 maybe employed, a target electrode being provided behind each aperture toreceive the beam current passing therethrough. The target beam currentmay be utilized as the output current. Such construction difi'ersfunctionally from that illustrated and described in the sense of thecurrent variations in the output channels.

Also, although in the constructions illustrated and described the beamtrace includes radially extending portions, such as BA1 in Fig. 4, thetargets may be arranged and the beam defiecting system correlatedtherewith so that such portions as BAl of the trace are other thanradial whereby additional guard space is introduced between adjacenttarget electrodes.

It will be understood further that the specific construction shown anddescribed is but illustrative of the invention and that variousmodifications may be made therein without departing from the scope andspirit of this invention as defined in the appended claims.

What is claimed is:

1. Electron discharge apparatus comprising a plurality of elongatedtargets arranged in a circle and extending at oblique angles torespective radii of said circle, means for projecting an electron beamtoward said targets, and means for sweeping said beam over said targetsin succession and in the direction, at each target, of the lengththereof.

2. Electron discharge apparatus in accordance with claim 1 wherein saidtargets are secondary electron emissive, the apparatus comprising alsocollector electrode means for receiving secondary electrons emanatingfrom said targets.

3. Electron discharge apparatus comprising means for projecting anelectron stream, means for deflecting said stream to produce a circular,saw-tooth trace at a preassigned region, and a plurality of targets atsaid region, said targets extending along respective alternate sectionsof said trace.

4. Electron discharge apparatus comprising a plurality of like,rectangular targets mounted in a circle and extending at equal obliqueangles to respective radii of said circle, means for projecting anelectron beam toward said targets, and means for deflecting said beam tosweep it over said targets in succession and in the direction of thelength of each target.

5. Electron discharge apparatus comprising a row of targets eachinclined with respect to the direction of the row, means for projectingan electron beam toward said targets, and means for sweeping said beamover said targets in succession and in the direction, at each target, ofthe inclination thereof.

6. Electron discharge apparatus comprising a plurality of elongatedtargets mounted in aligned, laterally adjacent relation and inclinedwith respect to the direction of alignment thereof, means for projectingan electron beam toward said targets, and means for subjecting said beamto a saw-tooth deflecting field to sweep it over said targets insuccession and in the direction, at each target, of the length thereof.

7. Electron discharge apparatus in accordance with claim 6 wherein saidtargets have secondary electron emission coefiicients greater thanunity, the apparatus comprising also collector electrode means adjacentsaid targets for receiving secondary electrons emitted thereby.

8. Electron discharge apparatus in accordance with claim 7 wherein saidcollector electrode means comprises shield portions extending betweenadjacent targets.

9. Electron discharge apparatus comprising a plurality of substantiallyidentical elongated targets mounted in a circle and extending atsubstantially equal angles to respective radii thereof, an electron guncoaxial with said circle for projecting an electron beam toward saidtargets, and deflection means comprising coaxial deflecting electrodesintermediate said gun and said targets for rotating said beam toproduce, at the targets, a saw-tooth trace alternate sections of whichare substantially coincident with the longitudinal axes of adjacenttargets.

10. Electron discharge apparatus comprising an insulating disc, aplurality of target electrodes mounted by said disc and in circulararray, said target electrodes having a secondary electron emissioncoefiicient greater than unity, and a plurality of collector electrodes,one for each target electrode, mounted upon said disc, each of saidcollector electrodes being adjacent a respective target electrode andhaving a shield portion extending between two adjacent targetelectrodes.

11. Electron discharge apparatus comprising an insulating disc, aplurality of collector electrodes mounted by said disc and in circulararray, each of said electrodes having a base portion opposite one faceof said disc, and a plurality of target electrodes each overlying thebase portion of a respective collector electrode, each of said targetelectrodes having a secondary electron emission coefficient greater thanunity, and each of said collector electrodes having a shield portionextending between two adjacent target electrodes.

12. Electron discharge apparatus comprising a plurality of elongatedtargets mounted in a circle and inclined with respect to respectiveradii thereof, electron gun means for projecting an electron beam towardsaid targets, means for subjecting said beam to a deflecting field suchthat at the targets the beam trace is of sawtooth form and includes aplurality of sawtooth sections, one for each target and extending in thedirection of the length thereof, and control means for interrupting saidbeam at times corresponding to preassigned points on said trace.

ALVA EUGENE ANDERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,195,098 Skellet Mar. 26, 19402,265,848 Lewis Dec. 9, 1941 2,290,651 Peck July 21, 1942

